JP2011071211A - Method of measuring self-bias of processing object, and method and device for separating processing object using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of measuring self-bias of a processing object, and to provide a method and device safely and reliably separating a processing object in a stable state by reflecting the same in a separation condition. <P>SOLUTION: A self-bias measuring component 7 of a conductor is installed in the vicinity of an outer peripheral edge of a processing object 10 fixed on a static chuck 2 in a plasma processing chamber. A step of measuring the voltage of the self-bias measuring component 7 during plasma processing to the processing object 10, and feedback control for applying a voltage reverse to the voltage applied to the static chuck 2 and a voltage offset by the measured self-bias value to set an indirectly obtained self-bias voltage of the processing object 10 at 0 V by assuming the measurement voltage to be a value equal to the self-bias of the processing object 10 are executed. In the measurement of the voltage, a voltmeter 9 connected between a cooling stage 6 and the earth is used, and the self-bias of the processing object 10 in response to a status change of plasma processing is fed back to the separation condition of the processing object 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for detaching an object to be processed held by electrostatic attraction force, and in particular, a self-bias measurement method, a method for detaching an object to be processed on an electrostatic chuck using the measurement method, and a detachment for the same. Relates to the device.

  An electrostatic chuck (ESC) is widely used as a member that strongly fixes a semiconductor wafer to a semiconductor manufacturing apparatus that processes the wafer by dry etching, sputtering, CVD, or the like while maintaining the flatness of the semiconductor wafer. It is composed of a dielectric layer that is held in contact with the wafer, and an electrode that generates an electrostatic force for fixing and holding, and is used by being bonded and fixed on a cooling stage called a jacket having a cooling function. Ceramics and polymer materials are used for the dielectric layer.

  Conventional electrostatic chucks, when using ceramics such as aluminum oxide as the dielectric layer, have a binary or higher composition with titanium oxide added so as to exhibit optimum adsorption force in the operating temperature environment. In addition to the Coulomb force, which is a pure electrostatic force, a strong adsorption force is obtained by utilizing the Johnsen-Rahbek force that is generated when a very small current flows. Alternatively, an electrostatic chuck using polyimide or the like as a dielectric layer of a polymer material is also used.

As a method for detaching a wafer (object to be processed) with such an electrostatic chuck, conventionally, a method of releasing a charge in the wafer (reverse voltage) by applying a constant voltage having a reverse polarity to that at the time of adsorption to the ESC electrode, or a constant power. A method has been developed in which the charge in the wafer is released through the plasma at (static discharge plasma).
However, in the sputtering process, it is often difficult to always perform stable detachment due to factors such as a change in plasma state with time due to the amount of target used.

Further, as shown in FIG. 10, when the state of electric charge in the wafer 52 when the electrostatic chuck 50 is used in the sputtering apparatus,
(a) The same number of positive charges and negative charges are mixed in the wafer 52 before the process,
(b) When a voltage is applied to the ESC electrode 54, + and − charges in the wafer 52 are unevenly distributed, and the wafer is attracted to the electrostatic chuck 50 by Coulomb force.
(c) When plasma is generated, ions and electrons are exchanged between the plasma and the wafer 52 (there is an irradiation to the wafer and an electric charge that escapes from the wafer), and a voltage at which the effective current becomes zero ( Stable when the self-bias occurs on the wafer. This amount of charge varies depending on conditions such as target usage.
(d) Even if the plasma and the electrostatic chuck 50 are turned off, a part of the electric charge irradiated in the wafer 52 remains. Due to the adsorption force due to the residual charges, a separation failure of the wafer 52 occurs. Even when a reverse voltage is applied to the ESC electrode 54, the residual charge often does not escape.

For this reason, in the electrostatic chuck (ESC) 50, it is often difficult to safely detach the wafer 52, and when the detachment condition is bad, as shown in FIG. As a result, the wafer 52 is displaced or cracked. Therefore, it is important to detach the wafer 52 stably.
As a conventional wafer detachment method, as disclosed in Patent Document 1, after a voltage having a polarity opposite to that at the time of electrostatic attraction is applied to positive and negative electrodes in an electrostatic chuck plate, the current flowing through each electrode during lift-up From this, the amount of charge remaining in each electrode is measured individually, the amount of reverse voltage applied that makes the amount of residual charge equal is determined, and this applied amount is applied to the wafer, thereby eliminating the deviation of the electrostatic attraction force. There is a way.

Japanese Patent Laid-Open No. 11-330217

  As described above, as a wafer detachment method with an electrostatic chuck, a method of releasing a charge in the wafer (reverse voltage) by applying a constant voltage having a reverse polarity to that at the time of adsorption to the ESC electrode or plasma with a constant power is used. The method of releasing the charge in the wafer (static discharge plasma) has been developed, but it is difficult to always perform stable detachment due to factors such as the amount of target used and the plasma state changing over time. .

  Conventionally, the self-bias can be measured by connecting a capacitor directly to the backside of the wafer and measuring the voltage. However, during the sputtering process, there is no conduction between the front and back of the wafer, so the self-bias that occurs The bias was different on the front and back sides, and the voltage I wanted to measure could not be measured. Originally, it is correct to measure the surface, but it is impossible because it is a film formation process.

  Further, in the invention of the above-mentioned Patent Document 1, after applying a voltage having a polarity opposite to that at the time of electrostatic attraction, the residual charge amount is individually measured from the current flowing through each electrode, and according to the type of the object to be processed and the processing content. In advance, from the relationship between the amount of applied reverse voltage and the amount of residual charge after application, the amount of applied voltage at which the absolute value of the amount of residual charge of each electrode is substantially equal is obtained, Although it was applied, it was difficult to always perform stable separation in a plasma state that changes from moment to moment.

  The present invention has been made in view of the above-described problems, and a method for indirectly measuring the self-bias of the object to be processed, and further reflecting the result on the separation condition, in a stable state of the object to be processed. It is an object of the present invention to provide a method and apparatus that can be safely and reliably detached.

In order to achieve the above object, a self-bias measuring method for an object to be processed according to claim 1 is characterized in that the self-bias of the conductor is located near the outer periphery of the object to be fixed on the electrostatic chuck in the plasma processing chamber. Install measuring parts,
During the plasma processing on the object to be processed, the voltage of the self-bias measuring component that is considered to be equal to the self-bias value generated in the object to be processed by the electric charge irradiated from the plasma is measured. .

  In a preferred embodiment, in the self-bias measurement component, an exposed surface that receives charges from plasma is disposed at a position equivalent to a distance from a plasma generation region to the surface of the object to be processed.

Furthermore, in the method for detaching the object to be processed according to claim 3, a self-bias measuring part for a conductor is installed near the outer periphery of the object to be fixed on the electrostatic chuck in the plasma processing chamber, The step of measuring the voltage of the self-bias measuring component during plasma processing on the object to be processed and the measurement voltage was obtained indirectly, assuming that the measured voltage is equal to the self-bias of the object to be processed. Feedback control is performed to apply a reverse voltage of the voltage applied to the electrostatic chuck and a voltage offset by the measured self-bias value so that the self-bias value of the object to be processed becomes 0V. A process,
The self-bias of the object to be processed according to the change in the state of the plasma processing is fed back to the condition for detaching the object from the electrostatic chuck.

  In this detachment method, the feedback control step further generates a plasma for static elimination, measures the self-bias again, and in order to make the measured self-bias constant, the pressure in the plasma processing chamber (chamber pressure) ) And the object to be processed is detached from the electrostatic chuck in a state where the self-bias value becomes 0V.

  An apparatus for detaching an object to be processed according to claim 5 is provided in the plasma processing chamber, and an electrostatic chuck plate for mounting and fixing the object to be processed that receives charges irradiated from the plasma on the upper surface. A self-bias measuring component for a conductor installed near the outer periphery of the workpiece fixed on the electrostatic chuck plate, and a cooling flow path that supports the electrostatic chuck plate and communicates with a cooling source A cooling stage, and a measuring circuit connected between the cooling stage or the self-bias measuring component and ground, and measuring a voltage of the self-bias measuring component during plasma processing on the object to be processed, The measured voltage is assumed to be a self-bias value generated in the object by the electric charge irradiated from the plasma, and the self-bar of the object to be indirectly obtained is assumed. A feedback control device for applying a reverse voltage of the voltage applied to the electrostatic chuck and a voltage offset by the measured self-bias value so that an asperity value becomes 0V; To do.

  According to the first aspect of the present invention, since the self-bias measuring part of the conductor is installed near the outer periphery of the object to be processed, the object to be processed is measured by measuring the voltage of the self-bias measuring part measured during the plasma processing. The self-bias can be obtained indirectly.

  According to the second aspect of the present invention, the distance from the plasma to the self-bias measuring component is equal to the distance from the plasma to the object to be processed, so that the amount of charge from the plasma irradiated on each surface becomes equal. A more accurate self-bias value can be measured.

  According to the third aspect of the present invention, the self-bias value of the object to be processed can be indirectly obtained by measuring the voltage of the self-bias measuring component, and the electrostatic chuck is set so that the self-bias value becomes 0V. The object to be processed can be safely and reliably detached from the electrostatic chuck by feedback control in which a reverse voltage of the applied voltage and a voltage offset by the self-bias value are applied.

  According to the invention of claim 4, the self-bias is generated again by generating the plasma for static elimination, and the pressure in the plasma processing chamber is changed in order to make the measured value constant. The object to be processed can be detached from the electrostatic chuck while the value is reliably set to 0V.

  According to the invention of claim 5, the self-bias value of the object to be processed can be indirectly measured by the self-bias measuring component, and only the reverse voltage of the voltage applied to the electrostatic chuck and the measured self-bias value. By using a feedback control device that applies an offset voltage, it is possible to provide a device that eliminates the residual charge of the object to be processed and allows the object to be removed from the electrostatic chuck safely and reliably.

(Aspect of the Invention)
In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention. In the following paragraphs, (1) corresponds to claim 1, (2) corresponds to claim 2, (6) corresponds to claim 3, and (7) claims. This corresponds to item 4, and item (8) corresponds to claim 5.

(1) A self-bias measurement part for the conductor is installed near the outer periphery of the workpiece to be fixed on the electrostatic chuck in the plasma processing chamber.
During the plasma processing on the object to be processed, the voltage of the self-bias measuring component that is considered to be equal to the self-bias value generated in the object to be processed by the electric charge irradiated from the plasma is measured. A method for measuring the self-bias of a workpiece.

  In the invention of the above (1), since the self-bias measurement component is installed near the outer periphery of the object to be processed, the measurement component is equivalent to the amount of charge received from the plasma by the object to be processed. By measuring this voltage, the self-bias value of the object to be processed can be indirectly measured.

(2) The self-bias measurement component is characterized in that an exposed surface that receives a charge from plasma is disposed at a position equivalent to a distance from a plasma region to the surface of the object to be processed (1) The measuring method according to item.

  In the invention of the above (2), the amount of charge received by the self-bias measuring component depends on the electron temperature of the plasma, that is, the energy, so the exposed surface of the measuring component is the distance from the plasma region to the surface of the object to be processed. , The amount of charge applied to the surface is equal, so the self-bias value is also equal.

(3) The self-bias measurement component is formed of a concave annular body that is engaged with and attached to the side surface of the electrostatic chuck plate, and the outer peripheral portion of the annular body protrudes upward from the surface of the object to be processed. The detachment method according to item (1), comprising:

  In the invention of (3) above, in the self-bias measurement component, the amount of charge applied to the exposed surface from the plasma generation region is equal to the amount of charge applied to the surface of the object to be processed. The self-bias value of the object to be processed can be indirectly obtained by measuring the voltage. Moreover, since the exposed surface is located at a position protruding upward from the surface of the object to be processed, the object to be processed is surrounded by the concave annular body, so that the displacement of the object to be processed can be prevented.

(4) The self-bias measurement component is formed of a concave annular body that is attached to be engaged with a side surface of the electrostatic chuck plate, and an outer peripheral portion of the annular body projects upward from the surface of the object to be processed. The removal method according to item (1), characterized in that the protrusion extends radially inward so as to cover the outer peripheral edge of the object to be processed.

  In the invention of the above (4), similarly, the self-bias value of the object to be processed can be indirectly obtained by measuring the voltage of the self-bias measuring component. Further, since the exposed surface protrudes upward and covers the outer peripheral edge (edge) of the object to be processed, film formation does not occur at the position shift and the edge of the object to be processed.

(5) The self-bias measurement component is formed of a concave annular body that is attached to be engaged with a side surface of the electrostatic chuck plate, and an outer peripheral portion of the annular body projects upward from the surface of the object to be processed. The detachment method according to item (1), further comprising a lower end that extends radially inward from the protrusion so as to cover the outer periphery of the object to be processed and presses the outer periphery.

  In the invention of the above item (5), similarly, the self-bias value of the object to be processed can be indirectly obtained by measuring the voltage of the self-bias measuring component. Further, since the exposed surface protrudes upward and covers and suppresses the outer peripheral edge (edge) of the object to be processed, the position of the object to be processed is fixed and no film is formed on the edge.

(6) A self-bias measuring component for a conductor is installed near the outer periphery of the object to be fixed on the electrostatic chuck in the plasma processing chamber, and the self-bias measurement is performed during plasma processing on the object to be processed. Measuring the voltage of parts for
Assuming that this measured voltage is the self-bias value of the object to be processed, the voltage applied to the electrostatic chuck is set so that the indirectly obtained self-bias value of the object to be processed is 0V. Performing a feedback control to apply a reverse voltage and a voltage offset by the measured self-bias value,
A method for detaching an object to be processed, wherein a self-bias of the object to be processed according to a change in the state of the plasma processing is fed back to a condition for detaching the object from the electrostatic chuck.

  In the invention of the above (6), the self-bias value of the object to be processed can be obtained indirectly by measuring the voltage of the self-bias measuring component, and the electrostatic chuck is set so that the self-bias value becomes 0V. The object to be processed can be safely and reliably detached from the electrostatic chuck by the food back control in which the reverse voltage of the applied voltage and the voltage offset by the self-bias value are applied.

(7) The step of feedback control further generates a plasma for static elimination, measures the self-bias again, changes the pressure in the plasma processing chamber in order to make the measured self-bias constant, The removal method according to item (6), wherein the object to be processed is detached from the electrostatic chuck in a state where the bias value is 0V.

  In the invention of the above (7), in addition to the reverse voltage, the feedback control process further generates a plasma for static elimination, measures the self-bias again, and makes this measurement value constant. Since the object to be processed is detached from the electrostatic chuck in a state where the pressure in the plasma processing chamber is changed and the self-bias value becomes 0 V, the position deviation of the object to be processed and the abnormal separation of cracks do not occur.

  Further, since the chamber pressure does not significantly affect the film formation rate, the residual charge in the object to be processed can be reduced without changing the film thickness on the object to be processed.

(8) An electrostatic chuck plate disposed in the plasma processing chamber for mounting and fixing an object to be processed that receives electric charges irradiated from plasma on the upper surface, and an object to be processed fixed on the electrostatic chuck plate A self-bias measurement part for a conductor, which is installed near the outer periphery of the body, a cooling stage which supports the electrostatic chuck plate and has a cooling channel communicating with a cooling source, and the cooling stage or the self-bias A measurement circuit that is connected between the measurement component and ground and measures the voltage of the self-bias measurement component during plasma processing of the object to be processed, and the measured voltage is irradiated from the plasma Assuming that the self-bias value generated in the object to be processed by electric charge is such that the self-bias value of the object to be processed obtained indirectly is 0V. And reverse voltage of the voltage applied to the click, release gear of the object, characterized in that it comprises a feedback control unit for applying the offset by the voltage of the measured self-bias value.

In the invention of the above (8), the self-bias value of the object to be processed can be indirectly measured by the self-bias measuring component, and only the amount of the reverse voltage of the voltage applied to the electrostatic chuck and the measured self-bias value. Since the residual voltage of the object to be processed is eliminated by applying the offset voltage, the object to be processed can be safely and reliably detached without causing an abnormal separation of the object to be processed.
(9) Furthermore, the configuration content of any one of the above-mentioned items (2) to (5) and (7) can be added to the configuration of the item (8).

(a) is a principle block diagram of the first embodiment for explaining a self-bias measurement method for an object to be processed according to the present invention, and (b) is a diagram showing other components for self-bias measurement used in this measurement method. FIG. 6C is an enlarged cross-sectional view showing still another form of the self-bias measurement component. It is a schematic explanatory drawing which shows the generation | occurrence | production principle of the self-bias which shows the electric charge state received from a plasma, and the electric charge state generate | occur | produced with the electrode of an electrostatic chuck plate. It is a sequence diagram which shows the process sequence by the flow of the voltage change explaining the detachment sequence of the to-be-processed object which concerns on this invention. It is a figure for demonstrating the self-bias in the direct current | flow sputtering device which is another aspect of embodiment which concerns on this invention. It is a characteristic view which shows the change of the correlation of the direct-current power (current x voltage) and self-bias during plasma processing. It is a characteristic view which shows the change of the self-bias with respect to the argon flow rate supplied in a plasma chamber. It is a graph of the characteristic curve which shows the change of the residual charge with respect to a self bias. It is a graph of the characteristic curve which shows the change of the self-bias value with respect to the usage-amount of a target. It is a figure which shows transition of the residual charge in a to-be-processed body in this invention and the conventional detachment | desorption method. It is a schematic diagram which shows the change of the electric charge state generate | occur | produced between the electrostatic chuck and a wafer in a prior art example. It is a schematic diagram which shows the detachment | leave state which generate | occur | produces with a push-up pin at the time of detachment | leave operation | movement of the wafer mounted on the electrostatic chuck plate of a prior art example.

Embodiments of the present invention will be described with reference to the drawings.
The present invention indirectly measures the self-bias generated by the charge irradiated from the plasma to the object to be processed such as a semiconductor wafer, and reflects the result in the separation condition, thereby enabling stable and safe wafer separation. Includes a composition that becomes.

  In FIG. 1, a detachment apparatus 1 according to the present invention is used, for example, in an etching apparatus or a sputtering apparatus, and an electrostatic chuck apparatus 2 is disposed in an airtight plasma processing chamber. The processing chamber 3 is generally composed of a cylindrical container made of SUS (stainless steel) or the like, and is itself grounded to the ground.

  As in the conventional structure, the electrostatic chuck device 2 is here in a state in which the electrostatic chuck plate 5 in which a pair of positive and negative electrodes 4 are incorporated and the electrostatic chuck plate 5 below the electrical chuck plate 5 are not electrically connected. And a cooling stage 6 as a support (susceptor) that supports the electrostatic chuck plate 5.

  The electrostatic chuck plate 5 has a structure having the pair of electrodes 4 described above. However, as one electrode, for example, a conductive layer is sandwiched between two polymer polyimide films. By applying a DC high voltage of, for example, 1.5 kV from a high-voltage DC power source installed outside the plasma processing chamber, the object to be processed 10 placed on the electrostatic chuck plate surface 5a is caused by Coulomb force. It may be a structure that is held by adsorption.

  The cooling stage 6 is bonded and fixed to the electrostatic chuck plate 5 and has a cooling flow path for communicating a cooling medium supplied from a cooling source (not shown). Although illustration is omitted here for the sake of simplicity, a push-up pin is inserted into the electrostatic chuck plate 5, and the workpiece 10 is moved by a drive mechanism (not shown) of the push-up pin. It is made to detach | leave from the electrostatic chuck plate 5.

  Further, the detaching device 1 of the present invention is configured to apply the voltage of the self-bias measuring component 7 composed of a concave annular body formed of a conductor attached around the side surface of the electrostatic chuck plate 5 and the self-bias measuring component 7. Assuming that the measurement circuit 11 for measurement and this measurement voltage are self-bias values generated in the object to be processed 10 by the electric charge irradiated from the plasma, the self-bias value of the object to be processed 10 obtained indirectly is assumed. Is a feedback control device (not shown) that applies to the electrostatic chuck plate 5 a reverse voltage of the voltage applied to the electrostatic chuck plate 5 and a voltage that is offset by the measured self-bias value. ).

The self-bias measurement component 7 is generally made of stainless steel, aluminum, titanium, or the like.
This self-bias measuring component 7 is for indirectly measuring the self-bias of the object 10 to be processed, and is installed near the outer peripheral edge 10a of the object 10 to be fixed on the electrostatic chuck 2. It consists of a concave annular body surrounding the processing body 10.

As shown in FIG. 1A, the concave annular body measuring part 7 has a shape in which the annular body outer peripheral portion 7 a protrudes upward from the surface of the workpiece 10.
Further, as a modified example of the concave annular body, as shown in the enlarged sectional view of FIG. 1B, the annular body outer peripheral portion 7a protrudes upward from the surface of the object to be processed 10, and the object to be processed is projected from this protrusion. It has a surface 7c that extends inward in the radial direction so as to cover the outer peripheral edge, and that inclines downward from the flat surface 7b.

  As another shape, as shown in FIG. 1 (c), the annular body outer peripheral portion 7a protrudes upward from the surface of the object to be processed 10, and the radial direction so as to cover the outer peripheral edge of the object to be processed from this protrusion. It has a lower end 7d that extends inward and presses the outer peripheral edge of the object 10 to be processed.

  In the self-bias measurement component 7 having these shapes, the amount of charge applied to the exposed surface from the plasma generation region 12 is equivalent to the amount of charge applied to the surface of the object 10 to be processed, and the self-bias measurement component The self-bias value of the object to be processed 10 can be obtained indirectly by measuring the voltage 7.

  Therefore, the exposure of the self-bias measuring part 7 is adjusted in accordance with the spherical shape of the plasma generation region 12 so that the distance from the plasma to the self-bias measuring part 7 is equal to the distance from the plasma to the object 10. The surface is located above the surface of the object 10 to be processed, and the amount of charge from the plasma irradiated on each surface becomes equal, so that a more accurate self-bias value can be measured indirectly. .

  In addition, the amount of charge received on the surface of the object to be processed 10 by the plasma irradiation corresponds to the electron temperature of the plasma, that is, the strength of the energy. It is desirable that the surface area of the upper surface of the bias measurement component 7 is the same as the surface area of the surface of the workpiece 10.

  Therefore, as shown in FIGS. 1B and 1C, the exposed surface of the self-bias measuring component 7 has a downward inclined surface 7c from the flat surface 7b of the outer edge to the inner side in the radial direction. This further increases the surface area. In the embodiment of the present invention, the concave annular body is used. However, the shape is not limited to the above shape, and the self-bias depends on the electron temperature of the nearby plasma regardless of the volume of the measurement component 7. As long as the position is close to the object to be processed, a measuring part having a volume and capacity different from the shape of the object to be processed 10 may be used.

  The exposed surface in FIG. 1 (a) is located at a position protruding upward from the surface of the object to be processed 10, and the object to be processed 10 is surrounded by the concave annular body, so that the positional displacement of the object to be processed 10 is prevented. be able to. In addition, the exposed surface in FIG. 1B protrudes upward and covers the outer peripheral edge (edge) of the object to be processed 10, so that the positional displacement and edge of the object to be processed 10 do not cause film formation. Further, the exposed surface of FIG. 1 (c) protrudes upward and covers and presses the outer peripheral edge (edge) of the object 10 to be processed, thereby fixing the position of the object 10 and forming a film on the edge. There is no.

  The measurement circuit 11 constitutes a voltage measurement circuit in which a resistance 8 of 1 MΩ or more and a voltmeter 9 are connected in parallel between the lower end of the cooling stage 6 and the ground (shield). Note that the measurement circuit may measure the voltage in such a manner that it is directly connected to the self-bias measurement component 7 without going through the cooling stage 6.

On the other hand, the resistance between the object to be processed 10 and the ground via the plasma is almost negligible with respect to the 1 MΩ resistance 8 of the measurement circuit, so the voltage measured by the voltmeter 9 is self-bias measurement. Is approximately equal to the voltage applied to component 7.
The self-bias measurement component 7 and the object to be processed 10 have the same irradiation distance from the plasma, and the surface area of the exposed surface facing the plasma is also formed to be equal. Since the amounts are substantially equal, the measurement voltage of the self-bias measurement component can be regarded as a value equal to the self-bias generated in the object to be processed during the plasma processing.
This self-bias value is fed back to the feedback control device, and is controlled so that the self-bias value generated according to the temporal change in plasma state becomes 0V.

Below, the self-bias measurement of the to-be-processed object 10 in the sputtering process using the said electrostatic chuck apparatus 2 is demonstrated as a plasma process.
As shown in FIG. 2, generally, a high DC voltage is applied to a pair of positive and negative electrodes 4 provided in the electrostatic chuck plate 5, and in accordance with the positive charges and negative charges generated at the electrodes 4, Negative charges and positive charges are unevenly distributed in the processing body, and the target object 10 is attracted and held on the surface of the electrostatic chuck plate 5 by Coulomb force. Then, the surface of the object to be processed 10 in the plasma processing chamber is irradiated with ions and electrons (e ⁻ ) from the plasma during the plasma processing. For this reason, charges remain on the object to be processed, and a negative voltage (self-bias) is generated by the amount of charges.

  Although it is very difficult to measure this negative self-bias during the sputtering process, in the present invention, it is considered that a self-bias similar to that of the object to be processed is also generated around the object to be processed. The self-bias measurement component is formed so that the object surface affected by the plasma is located at approximately the same distance and has the same exposed surface area, and the voltage is measured. This makes it possible to measure the self-bias of the object to be processed.

The procedure is shown below.
(1) A conductive self-bias measurement component 7 is installed near the outer periphery of the workpiece 10 held on the electrostatic chuck plate 5 supported by the cooling stage 6.
(2) During the plasma treatment (sputtering treatment) on the workpiece 10, the voltage of the self-bias measurement component 7 is connected in parallel to the voltage measurement circuit 11 (1 MΩ or more resistor 8) connected between the cooling stage 6 and the ground. Measure with a connected voltmeter 9).
(3) The measured voltage is regarded as a value equal to the self-bias generated in the object to be processed 10 by the electric charge irradiated from the plasma, and is fed back to the feedback control device as a condition for detaching the object to be processed 10.
As a result, the self-bias value of the workpiece 10 is indirectly measured by measuring the voltage of the self-bias measuring component 7.

Conventionally, the self-bias is measured by connecting a capacitor directly to the back side of the wafer and measuring the voltage. However, since there is no conduction between the front and back of the wafer during the sputtering process, the generated self-bias is Unlikely, the voltage to be measured could not be measured. Originally, it is correct to measure the surface, but it is impossible because it is a film formation process. For this reason, in the present invention, the self-bias on the wafer surface can be indirectly measured by installing a measurement component in a portion exposed to plasma as in the wafer.
The self-bias of the object to be processed depends on the electron temperature of the nearby plasma, regardless of the volume of the measurement component. Is obtained.

Next, with reference to FIG. 3, a method of detaching the target object 10 held by the electrostatic chuck 2 by reflecting the self-bias value based on the measured voltage in the detachment condition of the target object will be described.
As the separation operation of the object to be processed, the application of the ESC reverse voltage and the neutralization plasma are optimally performed. These conditions are changed according to the self-bias value. Conventionally, since the separation was performed under a certain condition, the object to be treated could not be detached stably even if the plasma state changed.

The optimum procedure of the present invention will be described below.
(a) Before the sputtering process, the voltage of (ESC + = + V, ESC − = − V) is applied to the electrodes of the electrostatic chuck 2 to attract the object 10 to be processed.
(b) Sputtering is performed, and at this time, the voltage of the self-bias measuring component 7 having a value equal to the self-bias (−S) of the workpiece 10 is measured by the method (2).
(c) After sputtering, a reverse voltage is applied to the electrode of the electrostatic chuck 2. However, the voltage is offset by the self-bias value (ESC + = − V + S, ESC − = + V + S).
(d) Generate plasma for static elimination and measure the self-bias again by the method (2) above.
(e) Change the chamber pressure so that the measured self-bias becomes a constant value.
(f) Wait until the self-bias value is completely 0V.
(g) The workpiece 10 is detached from the electrostatic chuck plate 5 with a push-up pin.

In the above process, when the residual charge is small after step (c), the process of steps (d) and (e) can be omitted and the process can proceed to step (f).
By the above procedure, as a first step, the electrostatic chuck 2 is applied so that the self-bias value of the object to be processed 10 obtained indirectly is 0 V by reflecting the self-bias (−S) during the plasma processing. Feedback control can be performed by applying a reverse voltage of the applied voltage and a voltage offset by the measured self-bias value. The object 10 can be reliably detached from the electrostatic chuck 2.

  However, the amount of residual charge accumulated in the object to be processed 10 changes depending on the change in the plasma state, and as shown in FIG. 5, the self-bias (absolute value) increases due to the increase of DC power during the plasma processing. Accumulated in the processing body 10.

  Further, as shown in FIG. 6, when the flow rate of Ar supplied into the plasma processing chamber is increased and the chamber pressure is increased, the phenomenon that the self-bias (absolute value) decreases is observed. There is an advantage that the self-bias can be changed without changing the film thickness because the film forming rate is not significantly affected.

  On the other hand, as shown in FIG. 7, when the relationship between the residual charge amount in the wafer and the self-bias is observed, the residual charge amount (absolute value) increases as the absolute value of the self-bias increases. In other words, the lower the self-bias absolute value during plasma processing, the smaller the residual charge amount in the object to be processed. This is considered to be a phenomenon that occurs because the residual attracting force of the target object 10 is generated by the residual charge in the target object due to self-bias during plasma processing and the residual charge of the electrostatic chuck.

Furthermore, as shown in FIG. 8, the self-bias (absolute value) tends to increase with time with respect to the amount of target used, and as a result, the residual charge of the object 10 is not constant. ing.
For this reason, in the optimum leaving method of the present invention, a series of steps (a) to (g) are executed.

  As described above, the detachment method of the present invention is characterized in that the self-bias of the object to be processed according to the state change of the plasma processing is fed back to the condition for detaching the object from the electrostatic chuck. In this separation method, the feedback control step further generates a plasma for static elimination, measures the self-bias again, changes the pressure in the plasma processing chamber in order to make this measured self-bias constant, In a state where the self-bias value is 0 V, the object to be processed is operated so as to be detached from the electrostatic chuck.

In addition, a control method in consideration of self-bias in a DC sputtering apparatus according to another embodiment of the present invention will be described with reference to FIG.
In a DC sputtering apparatus, a negative voltage is often applied to a target. Due to the characteristics of the plasma, a state is created in which the total current in the plasma becomes zero while electrons and ions diffuse and collide. In that case, the object to be processed is irradiated with electrons and ions, but as a result, a negative self-bias voltage is generated.

If the absolute value of the self-bias is reduced, the residual charge amount can be reduced. However, the conditions during sputter deposition cannot be easily changed.
Therefore, after sputtering film formation, first, an ESC reverse voltage is applied, and after removing the charge in the object to be processed and the charge in the electrostatic chuck plate to some extent, discharge plasma is generated to reduce the residual charge amount in the object to be processed. A two-step charge removal is performed to further reduce the charge.

Such reverse voltage or static elimination plasma results in the accumulation of electric charges, unless the optimum conditions are satisfied. For this reason, in accordance with the control procedure in the separation method of the present invention shown in FIG. 3, by reflecting the self-bias in the separation conditions, the object to be processed is detached stably and reliably without changing the film forming process conditions as much as possible. Can be made.
According to the detachment method of the present invention, the transition of the residual charge amount (absolute value) in the object to be processed with respect to the number of processed wafers has an absolute value and variation in the residual charge amount as compared with the conventional detachment method, as shown in FIG. You can see that it is getting smaller.

  DESCRIPTION OF SYMBOLS 1: Desorption apparatus, 2: Electrostatic chuck apparatus, 3: Plasma processing chamber, 4: Electrode, 5: Electrostatic chuck plate, 6: Cooling stage, 7: Self-bias measuring component, 7a: Annular outer peripheral part, 7b : Flat surface, 7c: downward inclined surface, 7d: lower end, 10: object to be processed, 11: voltage measurement circuit, 12: plasma generation region,

Claims (5)

A self-bias measurement part for the conductor is installed near the outer periphery of the workpiece to be fixed on the electrostatic chuck in the plasma processing chamber.
During the plasma processing on the object to be processed, the voltage of the self-bias measuring component that is considered to be equal to the self-bias value generated in the object to be processed by the electric charge irradiated from the plasma is measured. A method for measuring the self-bias of a workpiece.   2. The measurement according to claim 1, wherein the self-bias measurement component has an exposed surface for receiving a charge from plasma disposed at a position equivalent to a distance from a plasma region to the surface of the object to be processed. Method. A self-bias measuring component for a conductor is installed near the outer periphery of the object to be fixed on the electrostatic chuck in the plasma processing chamber, and the self-bias measuring component is installed during plasma processing on the object to be processed. Measuring the voltage;
Assuming that this measured voltage is equal to the self-bias of the object to be processed, an indirect obtained self-bias value of the object to be processed was applied to the electrostatic chuck so as to be 0V. Performing a feedback control to apply a reverse voltage of the voltage and a voltage offset by the measured self-bias value,
A method for detaching an object to be processed, wherein a self-bias of the object to be processed according to a change in the state of the plasma processing is fed back to a condition for detaching the object from the electrostatic chuck.   The feedback control step further generates a plasma for static elimination, measures the self-bias again, changes the chamber pressure in the plasma processing chamber to make the measured self-bias constant, and sets the self-bias value. 4. The detachment method according to claim 3, wherein the object to be processed is detached from the electrostatic chuck in a state where the voltage becomes 0V. An electrostatic chuck plate that is placed in the plasma processing chamber and that mounts and fixes the object to be processed that receives the electric charge irradiated from the plasma;
A component for measuring the self-bias of a conductor installed near the outer periphery of the object to be processed fixed on the electrostatic chuck plate;
A cooling stage that supports the electrostatic chuck plate and has a cooling channel communicating with a cooling source;
A measurement circuit connected between the cooling stage or the self-bias measurement component and ground, and measuring a voltage of the self-bias measurement component during plasma processing on the object;
Assuming that the measured voltage is a self-bias value generated in the object to be processed by the electric charge irradiated from the plasma, the self-bias value of the object to be indirectly obtained is 0V. And a feedback control device for applying a reverse voltage of the voltage applied to the electrostatic chuck and a voltage offset by the measured self-bias value.

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